More specifically, this invention relates to a stretch yarn having a composite core and a cotton fibres sheath; a preferred stretch fabric is denim.
There are several ways to make stretch fabrics in woven textile industry; mono stretch fabrics include elastic yarns only in warp or weft direction, in bi-stretch fabrics both in warp and weft directions elastic yarns are used.
The most common way of producing stretch fabric is weft (filling) stretch fabrics. Weft stretch fabrics have non elastic warp yarns and elastic weft yarns. In these fabrics different kind of elastic weft yarns such as corespun elasthane yarns, twisted elasthane yarns, intermingled or twisted synthetic elasthane yarns etc. are used. Elastic yarns are well known; the earlier fabrics, such as in U.S. Pat. No. 3,730,679 comprised stretch yarns that contained one elastomeric fiber and cotton fibers. These yarns provided fabrics with low recover after stretching: a typical elongation of these fabrics is of 15 to 40% in the weft direction, but the recovery characteristics are very low, usually as low as about 90% (ASTM D3107), i.e. the fabric has a growth of about 10%. To solve this problem, woven stretch fabrics comprising polyester bicomponent fibers have been disclosed, for example in U.S. Pat. Nos. 5,922,433 and 6,782,923. The fabrics disclosed in these references are comprised of bare bicomponent fibers and have strong synthetic appearance and hand due to the exposure of the bicomponent fibers on the fabric surface.
There is another way to make stretch fabric without using elasthane, in this type of fabrics usually elastic type of synthetic yarns are used like PBT, PTT or T400, i.e. a bicomponent PTT/PET.
Stretch denim fabrics made from a bi-component polyester and cotton are described in U.S. Pat. Nos. 7,310,932 and 5,874,372. However, fabrics made from elastic polyester lack good elasticity.
US 20080268734 discloses an elastic composite yarn comprising a core bi-component fiber in a cotton fibers sheath; the core comprises an elastic fiber and an inelastic fiber loosely wound around the elastic one. The purpose of the inelastic fiber is to improve the recovery properties of the yarn, so as to increase the recovery properties of the fabric including the above mentioned yarns. Drawbacks of this embodiment are that the inelastic fiber of the core is also acting as a block to the stretch of the elastic fiber and that the bundle of inelastic fibers appears through the cotton sheath in the final fabric.
The surfacing of the elastic core in the inelastic fibers sheath also occurs in other types of stretch yarns.
Therefore, there is the need to improve the known techniques and to provide a stretch yarn that can provide stretch fabrics with reduced fabric growth and still having a good stretch performance.